Field of the Invention
The present invention relates to compounds which inhibit phosphoinositide 3-kinases (hereinafter PI3K). In particular, the present invention relates to pyridazinone compounds, methods of preparing such a compound, pharmaceutical compositions which contain such a compound, and therapeutic uses of such a compound.
Discussion of the Background
In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates, a process referred to as phosphorylation. Specifically, PI3K enzymes are lipid enzyme kinases that can phosphorylate phosphoinositides (PIs) at the 3′-hydroxyl group of the inositol ring (see Panayotou et al, Trends Cell Biol 2:358-60 (1992), which is incorporated herein by reference in its entirety). It is well known that PIs, localized in the plasma membranes, can act as second messengers in signaling cascades by docking proteins containing pleckstrin-homology (PH), FYVE, PX and other phospholipid-binding domains (see Vanhaesebroeck B et al, Annu. Rev. Biochem 70, 535-602, 2001; Katso R et al, Annu. Rev. Cell Dev. Biol. 17, 615-675, 2001, both of which are incorporated herein by reference in their entireties). Therefore, PIs can act as second messengers in many cellular processes including signal transduction, regulation of membrane trafficking and transport, cytoskeleton organization, cell survival and death, and many other functions.
PIs may be bound to the lipid bilayer of the cell membrane via two fatty acids that are attached to the cytosolic inositol ring via a glycerol phosphate linker. PIs inositol ring can be phosphorylated by PI3K enzymes, leading to the regulation of cellular growth, survival and proliferation. For this reason, PIs phosphorylation by PI3K enzymes is one of the most relevant signal transduction events associated with mammalian cell surface receptor activation (see Cantley L C, Science 296, 1655-7, 2002; Vanhaesebroeck B et al, Annu. Rev. Biochem 70, 535-602, 2001, both of which are incorporated herein by reference in their entireties).
The PI3K enzymes have been divided into three classes: Class I PI3K, Class II PI3K and Class III PI3K, on the basis of sequence homology, structure, binding partners, mode of activation, and substrate preference (see Vanhaesebroeck B et al, Exp. Cell Res. 253(1), 239-54, 1999; and Leslie N R et al, Chem. Rev. 101(8), 2365-80, 2001, both of which are incorporated herein by reference in their entireties).
Class I PI3K convert phosphoinositide-(4,5)-diphosphate (PI(4,5)P2) to phosphoinositide-(3,4,5)-triphosphate (PI(3,4,5)P3), which functions as a second messenger. The signaling cascade activated by the increase in intracellular levels of PI(3,4,5)P3 is negatively regulated through the action of 5′-specific and 3′-specific phosphatases (see Vanhaesebroeck B et al., Trends Biochem. Sci. 22(7), 267-72, 1997; Katso R et al, Annu. Rev. Cell Dev. Biol. 17, 615-75, 2001; and Toker A, Cell. Mol. Life Sci. 59(5), 761-79, 2002, all of which are incorporated herein by reference in their entireties).
Class II PI3K enzymes are the most recently identified class of PI3K and their exact function is still unclear. Class III PI3K enzymes consist of a single family member which is structurally related to Class I PI3K enzymes and appears to be important in endocytosis and vesicular trafficking. However, there is some evidence showing that Class III PI3K may be relevant in immune cell processes, such as phagocytosis and Toll-like receptor (TLR) signaling. Class I PI3K enzymes can be further divided in class IA and class IB on the basis of their activation mechanisms.
In more detail, Class IA PI3K enzymes comprise three closely related isoforms: PI3Kα, PI3Kβ and PI3Kδ, while Class IB comprises only the PI3Kγ isoform. These enzymes are heterodimers composed of a catalytic subunit known as p110, with four types: alpha (α), beta (β), delta (δ) and gamma (γ) isoforms, constitutively associated with a regulatory subunit. The first two p110 isoforms (α and β) are ubiquitously expressed and involved in cellular differentiation and proliferation. Consequently, PI3Kα and PI3Kβ enzymes have been extensively studied as targets for the development of new chemotherapeutic agents.
Otherwise, p110δ and p110γ isoforms are mainly expressed in leukocytes and are important in the activation of the immune response, such as leukocytes migration, B and T cells activation and mast cells degranulation. Therefore, PI3Kδ and PI3Kγ isoforms are very relevant in inflammatory respiratory diseases and in cancer.
Presently, the inhibitors of PI3K enzymes known in the art could generally inhibit said isoforms (alpha α, beta β, delta δ and gamma γ isoforms) and they could act on the individual roles played in various diseases by said specific isoforms.
Therefore, specific activity assays of Class IA inhibitors for one specific PI3Kα, PI3Kβ, PI3Kδ and PI3Kγ isoform over another have been extensively developed in order to discern the suitable profile for the treatment of disorders associated with PI3K enzymes mechanisms. Such disorders could, for example, include respiratory diseases selected from idiopathic chronic cough, cough-variant asthma, cough associated with thoracic tumour or lung cancer, viral or post-viral cough, upper airways cough syndrome (UACS) or post nasal drip cough, or cough associated with gastro-oesophageal reflux disease both acid and non-acid, asthma, chronic bronchitis, chronic obstructive pulmonary disease (COPD), interstitial lung disease, idiopathic pulmonary fibrosis (IPF), congestive heart disease, sarcoidosis, infections (such as whooping cough), viral infections including viral respiratory tract infections and viral exacerbation of respiratory diseases; non-viral respiratory infections including aspergillosis and leishmaniasis; allergic diseases including allergic rhinitis and atopic dermatitis; autoimmune diseases including systemic lupus erythematous, rheumatoid arthritis and multiple sclerosis; inflammatory disorders including inflammatory bowel disease; cardiovascular diseases including thrombosis and atherosclerosis; hematologic malignancies; neurodegenerative diseases; pancreatitis; multiorgan failure; kidney diseases; platelet aggregation; cancer; sperm motility; transplantation rejection; graft rejection; lung injuries; and pain including pain associated with rheumatoid arthritis or osteoarthritis, back pain, general inflammatory pain, post hepatic neuralgia, diabetic neuropathy, inflammatory neuropathic pain (trauma), trigeminal neuralgia and central pain.
In view of the number of pathological responses which are mediated by PI3K enzymes, there is a continuing need for inhibitors of PI3K enzymes which can be useful in the treatment of many disorders. Thus, the present invention relates to novel compounds which are inhibitors of PI3Kα, PI3Kβ, PI3Kδ, and PI3Kγ isoforms of Class I PI3K enzymes that, for the above reasons, may often have therapeutically desirable characteristics. Particularly, compounds of the present invention may have much more selectivity for the δ isoform of PI3K enzyme over other isoforms of the same enzyme.